Calculating Coulomb interactions in molecular dynamics simulations: The Evjen method revisited

Area of Science:

• Computational Chemistry
• Materials Science
• Physics

Background:

• Accurate computation of Coulomb interactions is crucial for molecular dynamics simulations.
• Existing methods like the Ewald method have limitations in implementation and applicability.
• The Evjen method provided an early real-space approach but required extensions.

Purpose of the Study:

• To introduce a new direct summation (DS) method for calculating Coulomb interactions.
• To extend the DS method to handle noncubic unit cells and lamina systems.
• To evaluate the accuracy and efficiency of the DS method compared to the Ewald method.

Main Methods:

• The direct summation (DS) method, an extension of the Evjen method with unit cell dipolar correction.
• Real-space summation of truncated point charge interactions on a unit cell basis.
• Extension of DS theory for noncubic unit cells and lamina systems with 3D charges and 2D periodicity.

Main Results:

• The DS method demonstrates comparable accuracy and computational efficiency to the Ewald method for moderately sized systems.
• The DS method is effective for both bulk phase and lamina systems.
• The method is formally exact and has no adjustable parameters.

Conclusions:

• The DS method provides a robust and accurate approach for Coulomb interactions in molecular dynamics.
• Its real-space nature and straightforward implementation make it a valuable alternative to the Ewald method.
• The DS method is particularly useful for systems with noncubic unit cells and lamina configurations.